Field of the Art
The present invention relates to an arrangement in incinerators in which a fuel is burned in a fluidized bed of refractor particles, especially incinerators in which pipe coils for the circulation of a coolant are provided in the section of the incinerator in which the fluidized bed is located, said coils extending out through the shell of the incinerator.
Incinerators operating with a fluidized bed have many advantages, one being that they can burn a number of different fuels, including fuels of relatively low calorific value. When the incinerator is operating on high-grade fuels, e.g. oil, it may be desirable or necessary to cool the fluidized bed of refractory particles such as sand, and this cooling can be effected by means of a coolant circulating through pipe coils arranged in the fluidized bed. The ends of the pipe coils extend out through the shell of the incinerator to permit circulation of the coolant. The heat of the heated coolant may of course be utilized in various ways outside the incinerator. By changing the speed of the coolant and/or the temperature of the supplied fluidizing gas it is possible to achieve extensive accommodation to the calorific value of the fuel for maintenance of the desired heat balance in the fluidized bed.
When certain low-grade fuels are used, no cooling can be allowed. However, to stop the circulation of coolant in the pipe coils completely is not tolerable, since they may then burn out. In theory, it is feasible to remove the pipe coils when the incinerator is to be fired with low-grade fuels, but this usually involves an extensive and complicated modification of the incinerator.